专升本考试

【单选题】 ______ entering his flat, Jack was shocked to find his new computer missing.
A．In
B．On
C．By
D．At

网考网参考答案：B
网考网解析：
On+Ving，表“当做某事时”，即as soon as“一……就……”。 查看试题解析出处>>